Method of expanding piston skirts



1941- R. M. ULRICH 2,265,616

METHOD OF EXPANDING PISTON SKIRTS Filed Dec. 21, 1938 2 Sheets-Sheet 1Dec. 9, 1941. R. M. ULRICH 2,265,616

METHOD OF EXPANDING PISTON SKIRTS Filed Dec. 21, 1958 2 Sheets-Sheet 2[H 77b! Raymond M. U/r'l'clj of aU-slot piston;

Panes Dec. 9 1941 UNITED STATES PATENT OFFICE",

I METHOD OF PISTON SKI RTS Raymond Application December 21,

cylinder in the line 22 slightly'so as hack saw over an After a slot hasbeen formed. by sawingcase of thick-walled pistons as is the case inthinwalled pistona' v It is still another object of my invention toprovide an improved method of and means for the preparation ofexpansible pistons for the reception of the piston expander cooperatingwith the piston slot of the expansible skirt.

A still further object of my invention is to provide an improved methodof expanding the skirt The novel features which 'I believe tobecharacteristic of my invention are set forth with particularity in theappended claims. My invention itself, however, both as to itsorganization and method of operation, together with further ob- Jectsand advantages thereof, will be understood better by reference to thefollowing description taken in connection with the accompanying drawingsin which Fig. 1 shows a U-slot piston; Fig. 2 shows a perspective viewof my piston drill guide block; Fig. 3 shows the application of my drillguide block to the skirt of the U-slot piston; Fig. 4.is a detailed viewof the application of the drill guide block to the skirt of a piston;Figs. 5, 6, 7 and 8 are cross-sectional views which illustrate themanner in which the drill guide block cooperates with thin-walledpistons and with thick-walled pistons; Fig. 9 shows a perspective viewof one type of expander utilized in expanding the skirts of pistons;Fig. 10 shows a- U-slot piston in which an expander has been installed;Fig. 11 shows a perspective view of another type of piston expander;Fig. 12 shows a perspective I view of another type of piston drill guideblock; Fig. 13 shows the application of this modified form of drillguide block to the slot of a piston skirt; Fig. 14 explains theoperation of the drill guide block in connection with thin-walled pis-,of the drill.

tonsyFig. l5 explains the operation guide block in connection withthick-walled pistons, and Fig. 16 shows the expander of Fig. 11 insertedin a piston.

Referring to Fig. 1 of the drawings, I have'ilalong the line 22 of theM. Ulrich, Shelbyville, 111., .lllllfll' to Alois W. Graf, Strasbnrg,Ill. l

1938, Serial No. 247,089

lustrated therein a piston 20 of the U-slot type which is. provided witha ,U -slot 2| which permits the skirt to expand to a certain degree. Inorder to prepare the piston 20 for reception of a piston skirt expander,a substantially perpendicular line 22 is drawn from apoint approximatelymidway between the two sides of the U-slot 2 I .to the bottom. of theskirt. It is preferable to incline the to distribute the edge of theslot formed by sawing along the line 22 with 9. extended area-of thecylinder wall. with a hack saw along the line 22 a piston drill guideblockof the form shown in Fig. 2 is placed in position on this slot.

The piston drill guide block which is used is shown in Fig. 2 and itcomprises an elongated ody radius of curvature of which correspondsapprox imately to the radius of curvature of the more common pistons inuse. This concave surface 24 is provided with a body portion 22 so as toengage the'slot formed piston 20 shown in Fig. 1. At one extremitysuitable fastening means are provided comprising-a head member 21; aflat portion 28, a threaded portion 29 and a nut III which serves tomaintain the block 23 in proper operative position on the piston skirt.The head member '21 bears against the insidesurface of thepiston skirtwhile the flat portion 28 is located between the faces of the pistonslot. The body portion 22 is furthermore provided with a plurality ofdrill bit guides which are spaced apart ll l2 and 22, respectively, andextend from the concave surface 24 through the block 22,'the' axis ofeach guide forming an acute angle with the perpendicular to the tangentof the curvature of the concave face 24 at the center line extendingbetween the projections "and 28. The alternate axes of themembers 3|, tothe right and left of the drill bit cooperating produce concaveindentations in the faces ofv the slot which areoblique sections of acylindrical surface. Thus irrespective of the skirt wall thickness, eachpiston skirt is drilled atthe slot in a plurality of placesv spaced atfixed distances, from each other and from the slot, alongjthe outercircumferenceof the piston skirt- Fig.3 shows the drill guide block 23in operative rela- 22 and flare so placed the center line so that tionwith respect to the piston skirt of the piston Just slightly below aline drawn from one end of portion 23 having a concave face 24, the

pair ofprojections 2'5 and 2|; located adjacent opposite ends of theelongated within the guide will 20. The drill bit guide 32- is placed soas tobe the U-slot. 1 jiiwmpontheskirt'of the piston 20 and from v ofthe angles formed by'these-planes are at a point within the areapistonskirt:

i in?! exert the caseinthickwalledpiston skirts; V

. Figs. 7 and I; are sectionalfviews respectively along so that thecenter. of'the biasing force exerted by the expander comesslightl'yhelow the-:ends of Fig. 4 shows an viewof the fliisWiew-it willbecome apparent that the axes di -the driitbitvguldes ll and II areinthe same plane winch is at an acute angle to the right'of a planeperpendicular to a plane tangent to the curvatur of the piston skirtatthe slot, whereas na sa ers line perpendicular to the plane of 'the amof the means of the drill' bit guide :2 is in aplahe' which is at anacute angle to the left of the plane p rp ndicular to a plane tangent tothe curvature of'the piston skirt at the slot 22'. The vertices 5FromFigs. 5 and- 6 which are respectively see tional views along; thelines "A's-A and B-r- 1' I Fig. 4. it will be seen that in a thin-walledpiston skirt the inside view of the arcuate indentations in the faces oftheslot would represent indenta;-.

' tionsin sta gered relation so that if tangents to theindentationslwereI ould spacedlgapart an appreciable m m ll i t the e as greata. tensionon the piston to thefaces of the piston-sloth, I

7 expander suchfas shown in. Fig. 9 winner.

ody. Fig. 10 discloses a U-slot'piston having an ex pansible skirtprovided with a slot 22' therein.

The faces of the slot 22 have indentations there-J- irr-ri hichhavesurfaces corresponding to oblique sections of a cylindrical surface andeach surface hasan axis which is at an acute angle to the per-*pendicular to the tangent of the surface of the piston skirt at theslot. The expansible skirt of the piston which is normally provided witha slot 22' in accordance with the method previously set forth hasindentations 40, ll and 42 on the faces thereof which are formed by thedrill co-' operating with the drill guides 3|, 32 and 33 re-' spectivelyof the piston drill guide block 23. An "expander" of the type shown at39 is shown in- V serted in these indentations sothat the projections35, 31 an'd 38, respectively, extend into the indentations 40, 4| and42, respectively. The

expander 14 is inserted into these indentations by v grasping the lowerend of the. expander adjacent on thelinside, of the; to'theflat portion39 with a pair: of pliers, insert-J ing projections Y35 and intothellndentations indentation 5 2.? Thelfiat; end portions 38 and 39 ofthe body member of theexpander now serve the u e; A-A and or Fig. i inthe ins nce where thick-walled pistons are utilized v In this instanceit willbelipparmflfrom' the that 1 when viewed tromthe ofa the arcuateindentations will .appearito be more nearly in line and hence thetangents to'theindentations are drawn parallel to the piston slot ionthe.

inside, of the piston 'skirt; 7 'These indentations willbefclosertosether than was in a thin walled piston, an expander of'afixed or a non-adiustable-type suchasshown in h j 9, when intheindentations thus made 1' will exert a greater force on a thick-walledpiston than on a thin-walled pistons. The angles; at which the drill bitguides ,3! and have been arranged are so chosen that-anvexpander of thethin-walled and thick-walled piston skirts. no; compensation oradjustment is required on the part ofthe person installing theseexpanders to pr cvi de'for thevariations inthe thicknesses of. P1 -C-.g. 9 of the' drawings, I haveillteferring to I lustrated therein'oneembodiment of my piston expander comprising arcuate-shaped body memberpreferably of; springfsteelgprovided 1 with a'plurality of '-proiectionsor lugs 15 andv 3i 7 in theproximity of theends ofLthebody member and aprojection or lug 31 at an intermediate portion thereof; 7 Theprojections "and "near as bearingsurface's against the inside wall ofthe piston skirt thereby 'preventing any possible, change in theposition or shape of the expander, due.to temperature variations whichwould tend to cause the end projections 35 and 38 to extend r throughthe wall of the piston an undesired amount. The flat portions, and 39ing-the intermediate portions between the projections are thereforecontiguous to the inside wall; of the.

' piston skirt. Anexpanderof the type shown in Fig. 10 is particularlyadapt'eti to the expansion of U-slot pistons since the expansive forcealong 1 the piston slotifl' extendspver. a considerabledistance and thecenter of the force is slightly 1 below the lower extremities of theUV-slot 2i; 'In Fig. 11 I have shownanother form of fixed or non-'adjustable piston expander 43 which has i albody' member 44 arrangedin'a double reverse curve shape or, in other words, a shape having a?central or horseshoe-shaped portion and the e V ,sc-

' .itisapparent'that the single type 'of piston iexe pander produces theproper expansiongin both the endsof the-body 34 are set back a shortdis-5;.

tance from the extremities thereof so fastoleave fiat'portions 38 and",the purpose of which will subsequently become apparent. The projectingmembersil'it and 31 are'arranged substantially 'perpendicularto theplane'of the arc'of the .body

of the expander, but preferably at slight anglesito theperpendicular-{oi the plane so'that the curved outer'portions ofctheprojections, 35 and 31 ends of the U or horseshoe-shaped portion'areb'entback in reverse curves. Near the ends 45 of I the curved portion ofthe expander there are small portions l8 substantially at-rightanglesto'; the material adjacent the end and at right angles to thesmallportionli 'there are proiecv. -55 tions" which have convex bearingsurfaces. .The' projections 41 are arranged to engage inden'ta-: tionsalong the faces of the piston slot and the 1 flat'portions serve asinside bearing surfaces V g on; the inner .face [of the piston skirt.-If.-, at the center of the convex'surfaces ofthe pro- 7 iections .4!planes are drawn tangent thereto it: willbe found that the planes ofIthetWoprojec-L' tions 7": will form an 'acute anglerv Theproiecplaneperpendicular to'the plane of the body it of the expanderr In. Fig. 12 Ihave shown a piston drill guide? block having abody portion 48 which hasa con cave face theradiusof curvature of which cor-e. respondsapproximately to the radius ofcurva-lx. ture of thepistons more commonlyin, ,use. At 7 theupper-endof the concave'surface 49 there is J V i vprovided a projection 50 for thepurpose of en-J form slight angles tothe right and left of the. 7 gagingthe slot of the piston skirt; At theother 7 exams urine my a suitable fastening means are providedcomprising a head member a flat portion 52, a threaded portion"53 and anut 54 which serves to maintain the block 48 in proper operativerelation on the piston skirt. The head member 5 I, bears againsttl'ie'iaside surface of the episton skirtwhile the flat portion 52 islocated between the faces of the slot The bodyaportion I8 is furthermoreprovided with a plurality of drill bit guides 55. and 58, respectively,which are spaced apart and extend from the concave surface 43 throughthe block 48, the axis of each guide forming an acute angle with theperpendicular to the tangent of th curvature of the concave face 49 atthe center line extending between the projection ill and the aperturefor the fastening means 5| to H. The axes of the guides 55 and 56 are soplaced to the right and left of the center line that the drill bitscooperating within the guides will produce in the faces of the slotindentations which are oblique sections of a cylindrical surface. Fromthis it will be apparent that the method here utilized is the same asthat employed with the drill guide block of Fig. 2. Hence, irrespectiveof the skirt wall thickness, each piston skirt is drilled near the slotin a plurality of places spaced at fixed distances from the slot alongthe outer circumference of the piston skirt.

In Fig. 13 there is shown a portion 51 of a piston skirt, a piston skirtslot 58 and another portion 59 of the piston skirt. The drill guideblock 48 is shown in operative relation with respect to the piston slot58. From this view it will be apparent that the axes of the drill bitguides 55 and 56 have a common plane which, is substantially at rightangles to the piston slot 58. If planes along the axes of the drill bitguides 55 and I! are formed which are perpendicular to the common planeit will be found that these planes will form an acute angle somewhere tothe inside of the piston skirt.

Fig. 14 shows a sectional view along the line Y or plane (JP-C of Fig.13 in the instance where a thin-walled piston 'skirt is used. From thisview it will become apparent that the arcuate indentations in thefacesof the slot when viewed from the inside of th piston skirt arespaced apart an appreciable amount. If tangents to the indentations weredrawn on the inside of the skirt parallel to the faces of the slot 58they would be spaced apart an appreciable amount. Thus in thin-walledpiston skirts the expanders of the type shown in Fig. 11 will not exertas great a tension on the piston skirt as would be the case inthick-walled piston skirts.

Fig. 15 shows a sectional view along the line C--C of Fig. "13 in theinstance where thickwalled pistons are utilized. In this instance itwill be apparent from. the figure that when viewed from the inside ofthe piston skirt the arcuate indentations will appear tobe closertogether-than was the case in a thin-walled piston. Thus, an expandersuch as shown .in Fig. 11, when inserted in the indentations will exerta greater force on a thick-walled piston than on a thin-walled piston.The angles at which the drill bit-guides 5! and It havebeen arranged areso chosen that any expander of the type shown in Fig. 11 will alwaysproduce the proper biasing eflect against the slot faces of theindentations to produce the proper expansion fit of the piston withinthe piston cylinder.

Fig. l6 illustrates the manner in which an expanderof the type shown in11 is inserted in the indentations 60 and 6| which are formed in thefaces of the piston slot 58 by the drill bit guides 55 and 56. It willbe seen that the convex surfaces of the expander projection H are"complementary to the arcuate indentations 60 and GI which have concavesurfaces each comprising obliquesections of a cylindrical surface.

While I have shown and described rny invention in connection withcertain specific embodiments, it will, of course, be understood that Ido not wish to be limited thereto, since it is apparent thatmodifications may be made in the instrumentalities employed withoutdepartingjfrom the spirit and scope of my invention as set forth in theappended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The method of expanding by equal amounts slotted piston skirts ofdifferent thicknesses with a single size fixed expander located withinsaid skirt and provided with a plurality of projections engagingindentations formed in said slot without altering the outercircumferential distances between said indentations which comprisescontrolling the degree of biasing force applied by said expander byforming an indentation on one face of the slot by drilling at apredetermined acute angle to a plane perpendicular to the tangent of theskirt at the slot and forming at a fixed outer circumferential distancefrom said first indentation an indentation on the other face of the slotby drilling at an acute angle to the opposite side of said plane wherebythe circumferential distances betweensaid indentations on the inside ofsaid skirt decreases in proportion to the skirt thickness, said angleshaving vertices within said skirt, and biasing said skirt to expand itby engaging said indentations with said expander projections.

2. The method of expanding by equal amounts longitudinally slottedpiston skirts of difl'erent thicknesses with a single size fixedexpander which comprises drilling said skirt at said slot in a pluralityof places spaced at fixed distances along the outer circumference ofsaid skirt and at acute angles to the right and left of a planeperpendicular to the tangent of a piston at the slot to. form in oppositfaces thereof concave indentations, each having surfaces whichcorrespond to oblique sections of a cylindrical surface, said surfaceseach having an axis at an acute angle to said plane, said angles havingvertices on the inside of' said piston skirt, and applying biasingforces to said indentations on alternate faces of said slot indirections generally perpendicular to the surfaces of said indentations,said biasing forces being increased in proportion to increased thicknessof said skirt; a

3. The method of expanding a U-slot piston comprising forming alongitudinal slot in the piston skirt in the general direction of theaxis of the piston on the side adjacent to the U-slot,-

drilling said piston skirt at said slot at a plurality of places atfixed distances relative to the outer circumference of said skirt and atangles to the right and left of a plane perpendicular to the tangent ofthe piston at the slot thereby forming a plurality of concaveindentations on altb.

nate faces of said longitudinal slot, each inden-*- tation having asurface corresponding to an tations on alternate faces of said slot indirec- .tions generally perpendicular to thelsurfacels of.saidindentations. a 1: v 4. The method of expanding by equal amountsjslotted pistonskirtsot diilerent skirt wall thicknesses'with a singlesizeflxed expander hajving projections'thereon' and which isiadapted tobe located within said piston skirt which comprises controlling thedegree of biasing Iorce exerted by ,said expander-at the projectionsthereot'by drilling saidpistonskirt in a plurality. of places "spaced atfixed-distances alongfthe outer circumference of said "piston skirt .tothe right. and left of said piston skirt slot and-at acute angles to,the right and left ot a plane perpendicular to the tangent surfaces toexpand mum curvature of said piston skirt ae" slot ,thereof to formsurfaces which correspond to oblique sections of a cylindrical surface,sald surfaces each having an axis at an acute angle to said plane, saidangles having verticesron the inside ofsaid. piston" skirt whereby theinner circumferential distances between the surfacesformed will decreasein proportion to an increase in the skirt thickness to increase thee'flective biasing force of said expander, and applying the biasingforces of said expander projections in directions generallyperpendicular tov said formed said piston skirt; a RAYMOND M. ULRICH.

